1. Field of the Invention
The present invention relates to a solid support. More specifically, the present Invention relates to a solid support comprising a polypeptide which is immobilized on the surface of a carrier.
2. Description of Related Art
Genetic test for investigating the presence of pathogenic bacterial infection is carried out by determining the presence of nucleic acid derived from the pathogenic bacteria in a clinical sample collected from patient. The testing process comprises mainly the following 3 steps: (1) collecting of pathogenic bacteria (solution of cell); (2) bacteriolysis (extraction and purification of nucleic acid); and (3) gene amplification and detection. Yield of the pathogenic bacterial cell and/or the nucleic acid in each step affects greatly on sensitivity and accuracy of the test.
In the above-described step (1) of collecting a pathogenic bacteria, when, for example, tuberculosis bacteria is collected as the pathogenic bacteria, collection of the tuberculosis bacteria has been carried out conventionally by a high-speed centrifugal separation procedure. However, the high-speed centrifugal separation procedure is known to have the following problems: Firstly, in the high-speed centrifugal separation procedure, generation of aerosol tends to take place, and opening and closing operations of the sample container is required. Therefore, there is a possibility of cross-contamination to occur between samples, and in addition, there are concerns about biohazard such as contact infection of operator, environmental pollution and the like. Secondly, since the procedure requires a relatively large stand alone instrument of a high-speed centrifugal separator, it is difficult to automate a series of the above-described test steps in a continuous fashion. Thirdly, it takes long time for the high-speed centrifugation to attain a high recovery efficiency.
As an alternative method to such high-speed centrifugal separation procedure, a cell-collection technique for isolating pathogenic bacteria such as tuberculosis bacteria safely and easily within a short time using a solid support with polysaccharide as a ligand has been developed. It has been described that, in particular, when magnetic beads are used as a support (carrier), cell-collection can be performed easily by solid-liquid separation utilizing magnetic action (US-A-2003/153028).
In addition, in the above-described step (2) of bacteriolysis (extraction and purification of nucleic acid), after the bacterial cells collected by the step (1) or the like are lysed by a suitable method, nucleic acid is needed to be extracted and purified from the sample containing inhibitors of nucleic acid amplification reaction such as enzymes, other proteins, polysaccharides and lipids, and other contaminants. As to method for extracting a nucleic acid from a sample containing the same, for example, phenol/chloroform extraction method and the like have been used widely. After that, as a method for recovering the nucleic acid from a solution of phenol/chloroform extracts, ethanol precipitation method has been employed.
Further, method for purifying the extracted nucleic acid includes a method in which the nucleic acid is adsorbed on the surface of an adsorbent such as silica dioxide, silica polymer, magnesium silicate and the like, washed, and then the nucleic acid is desorbed (see, for example, JP-B-7(1995)-51065 and US-A-2004/235034). The method is excellent in separation performance of the adsorbent, however, the method has problems such as a difficulty in manufacturing the adsorbent with the same performance industrially on a large scale, and a difficulty in processing the adsorbent to various forms due to its inconvenient handling. And so, a method for separating and purifying nucleic acid has been developed, which comprises a step in which nucleic acid is adsorbed on or desorbed from a solid phase made of a surface-saponified product of acetylcellulose (an organic macromolecule having hydroxyl group on the surface) instead of the above-described adsorbents of silicon oxide type. According to the technology, it is stated that the surface-saponified product of acetylcellulose is excellent in separation performance, good in washing efficiency, and easy in workability compared with the adsorbent of silicon oxide type, and capable of being produced on a large scale with a substantially equivalent separation performance (US-A-2003/170664). However, in either method described above, there remain such problems that it is necessary to use chaotropic agent such as perchloric acid when the nucleic acid is trapped on the adsorbent, and further that a mixed solution of solubilized nucleic acid is required to be mixed with water-soluble organic solvent, and the resultant mixed solution of nucleic acid requires existence of a salt. A method of avoiding the use of hazardous reagent such as chaotropic agents by employing porous carrier (glass fiber, cellulose fiber, hydroxyapatite, and the like) capable of adsorbing nucleic acid has also been developed (JP-A-2005-80555). However, since the method comprises drying step, operation is cumbersome and requires large-sized equipment. On the other hand, in recent years, for the nucleic acid extracted from tissue, a method for recovering mRNA and the like by using a carrier on which an oligo dT sequence is immobilized, has been developed (US-A-2007/092576).
Aside from the above-described isolation techniques of nucleic acid from pathogenic bacteria, MDP1 (Mycobacterium DNA-Binding Protein 1) which is a polypeptide having immunogenicity against pathogenic acid-fast bacteria, and utilization thereof for a vaccine or a therapeutic agent has been disclosed (WO 2000/44905).